This invention relates to alkanesulfonamides and more particularly to a novel process for their preparation.
Synthetic methods for organosulfonamides in general and for alkanesulfonamides in particular are well known in the literature. Many of these involve treating the corresponding sulfonyl chloride with ammonia or a primary or secondary amine in the presence of various organic solvents. These prior art processes all provide an initially crude product which is contaminated with by-products and requires further purification before it can be used further.
The present invention provides a method for the synthesis of alkanesulfonamides which provides a number of advantages over previously reported procedures.
The present invention contemplates a direct synthesis of alkanesulfonamides from readily available starting materials. The sulfonamides recovered from the crude reaction mixture are sufficiently pure for use as synthetic intermediates without further treatment.
European Patent application 0276182 describes the preparation of C.sub.1 -C.sub.4 alkanesulfonamides using di- or mono- alkoxy alkane solvents. No equivalence to other solvents is suggested.
U.S. Pat. No. 3,300,529 describes a process for preparing N-alkyl and N,N-dialkyl-substituted ethylene- sulfonamides by simultaneous dehydrochlorination and amination of .beta.-chloro-alkanesulfonylchlorides in any unreactive solvent. Included in the general list of suitable solvents are tetrahydrofuran and "ether solvents" in general. No particular advantage for any particular solvent in the reaction at issue is pointed out. The use of any of the solvents in the preparation of saturated alkanesulfonamides is not discussed.
U.S. Pat. No. 3,781,441 describes a process for making 4-chloro-3,5-dinitrobenzenesulfonamide from the corresponding sulfonyl chloride by reaction with ammonia in various solvents at temperatures below 10.degree. C.
Included among the list of suitable solvents are C.sub.4 -C.sub.8 cyclic ethers. Tetrahydrofuran is specifically mentioned. Here the process of the patent is concerned with avoiding displacement of the aryl chlorine by ammonia. No particular advantage to the use of cyclic ethers such as tetrahydrofuran over any of the other listed solvents is stated.
U.S. Pat. No. 3,574,740 describes the preparation of methanesulfonamide and its derivatives by treating methanesulfonyl chloride in a C.sub.1 to C.sub.4 nitroalkane with ammonia or a primary or secondary amine. Substitution of other solvents is not suggested. As stated in this patent, the solubility of methanesulfonamide in nitroalkanes is highly temperature dependent, requiring that filtration to remove by-product be conducted at elevated temperature. In addition, processing in nitroalkanes produces discolored products. More complex processing is required by the necessity of conducting hot filtrations and removing undesired color from the product.
Czechoslovakia Patent 235,626 describes treatment of methanesulfonyl chloride in solution in toluene with gaseous ammonia followed by crystallization of the methanesulfonamide product from a toluene/ethanol mixture after concentration. Ammonium chloride is soluble in the toluene/ethanol reaction mixture described in the patent to over 1% by weight concentration. The product must be isolated by crystallization from the concentrated reaction mixture to separate it from the ammonium chloride remaining in solution. This results in a drop in yield to about 90%. On a large scale, this small drop in yield can have significant economic consequences. No other solvents are suggested as equivalents or as alternatives.
J. Am. Chem. Soc., Vol. 75, page 934 (1953), J. Am. Chem. Soc., Vol. 77, page 170 (1955), Monatsh., Vol. 89, page 285 (1958) as summarized in Chem Abstracts Vol. 53, Col. 1140i (1959) and J. Chem. Soc., Vol. 125, page 1463 (1924) all describe treatment of methanesulfonyl chloride in benzene with anhydrous ammonia to give the desired methanesulfonamide. No other solvents are suggested as suitable equivalents or alternatives.
Zhur. Obschei Khim., Vol 18, page 729 (1948) as summarized in Chem. Abstracts Vol. 43, Col. 120f describes treatment of methanesulfonyl chloride in dry diethyl ether with anhydrous ammonia followed by evaporation of solvent and extraction of the residue with benzene to obtain the methanesulfonamide product. Once again, other solvents are not suggested as suitable equivalents or alternatives.
Benzene is a known carcinogen and, while it can be handled industrially, its use complicates any process in which it is employed.
None of the teachings of these prior art references suggest to one of skill in the art of organic chemistry that an alkanesulfonyl chloride may be dissolved in the solvents comprehended by the instant invention and treated with anhydrous ammonia or with primary or secondary amines with the result that a substantially complete separation of ammonium chloride or amine hydrochloride is obtained from the desired alkanesulfonamide which may then be recovered in high purity and in extremely high yields (93% and greater) simply by evaporation of solvent.